A great variety of material is shipped in railroad cars having doors, or gates, at the bottom thereof for unloading material. Virtually any material that is capable of "flowing" can be shipped in such cars, and unloaded through the hopper doors. These materials include such diverse things as woodchips, gravel, sand, chemicals in powder form, and numerous other materials. The shipping in a hopper car is very convenient because the material can be easily loaded through the large open top of the car; then, when the car is to be unloaded, the car can be conveyed to tracks having open spaces therebetween, the hopper doors can be opened, and the material will flow from the car into any receptacle placed below.
The problem with the use of hopper cars is that, while the material may be flowable at the time the car is loaded, the contents are caused to settle by the bouncing and rocking during transportation so that the material is more densely packed on arrival. Also, the material may be rained on in transit and the additional moisture will cause some materials to stick with even greater tenacity.
Prior art means for unloading hopper cars where the material is compacted and stuck together so that the material will no longer flow through the hopper doors has included such means as augers to bore down and loosen the material, and vibrators placed against the side walls of the hopper car. With the vibrators, the hopper doors are opened, and the vibrators are energized causing the car to shake in order to loosen the material inside and urge it to flow through the open hopper doors. These vibrators are only somewhat successful because the material is frequently so firmly packed and cohesive that vibration of the car will not cause the material to flow. Augers have met with little commercial success, and are difficult and time-consuming to use. There are also devices to shake the entire car, and these devices are rather successful; however, shaking the entire car both requires an extremely large amount of energy and is highly detrimental to the car. Car shakers frequently exert such forces on the hopper car that rivets are loosened and seams break loose so that a railroad car will have to be repaired much more frequently. One of the more successful means for unloading hopper cars is the car inverter, whereby the entire car is turned upside down so that the contents are emptied through the large opening in the top thereof. While these devices are rather successful, the equipment required to invert the entire railroad car is extremely large, requiring a very large capital investment in addition to a very large operating cost because of the energy required to invert every railroad car.
It is known in the art to utilize a device known as a blast aerator to assist in material flow in bins; however, these blast aerators have been used only through the side walls of bins and a railroad car has never been provided with the necessary openings or brackets for mounting blast aerators. Thus, there has never been previously devised any means for utilizing a blast aerator in the unloading of a railroad car.